Expansion of e.g.f.: exp(-x) / cosh(2*x).

Terms

a(0) =1a(1) =-1a(2) =-3a(3) =11a(4) =57a(5) =-361a(6) =-2763a(7) =24611a(8) =250737a(9) =-2873041a(10) =-36581523a(11) =512343611a(12) =7828053417a(13) =-129570724921